An analytical method was used to estimate the Peierls-Nabarro barrier energy, γPN, for the relevant slip system in this intermetallic. The Peierls-Nabarro barrier energy and a generalized fault energy, γF, were combined, and used as a measure of dislocation

mobility. A fracture model was developed in order to describe the motion of thermally activated dislocations away from the crack tip and thus to predict the fracture resistance. A ductility index was defined in terms of the ratio of γs/(γPN+γF), where γs was the surface energy, and was used to correlate the fracture toughness values of intermetallics. This correlation indicated that the fracture toughness increased with increasing values of γs/(γPN+γF); in accord with a fracture model based upon thermally activated slip.

Relationships of Fracture Toughness and Dislocation Mobility in Intermetallics. K.S.Chan: Metallurgical and Materials Transactions A, 2003, 34[10], 2315-28

Table 2

Activation Volumes for Interdiffusion in FeAl